Diagnosing Spinal Stenosis

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NYU Langone spine specialists can determine the cause of spinal stenosis—a narrowing of the spinal canal, the hollow center of the spine that contains the spinal cord and nerves.

The spine consists of bones called vertebrae, which stack on top of one another and normally provide plenty of room for the spinal cord to pass through. In between each vertebra is an opening, called a foramen, through which nerves exit the spinal cord and travel throughout the body.

The rear parts of the vertebrae join in an interconnected system of joints that allow the spine flexibility and movement. In between the front part of each vertebra is a soft disc made of cartilage that acts as a shock absorber between the bones.

If the space within the spinal canal or foramen gets smaller, the spinal cord or nerves may be squeezed, interrupting nerve signals and causing tingling, weakness, or pain. Without treatment, spinal stenosis may lead to permanent nerve damage.

Stenosis may develop in any part of the spine, though it is most common in the lower back (lumbar spine) or in the neck (cervical spine). Because of the location of nerves as they exit the spine and travel throughout the body, lumbar stenosis typically causes weakness or pain in the legs, and cervical stenosis causes symptoms in the shoulder or arm.

Spinal stenosis is most often diagnosed in people between the ages of 50 and 80.

Symptoms of Lumbar Stenosis

Stenosis that occurs in the lumbar spine has a recognizable pattern of symptoms, including pain, heaviness, and weakness felt not in the back itself but in the buttocks and legs. Typically, lumbar stenosis causes few or no symptoms if you’re sitting or lying down, but symptoms become more significant when you’re walking or standing in one position for too long.

If nerve constriction caused by spinal stenosis progresses, symptoms may cause increasing discomfort, and the distance you can walk without pain and weakness diminishes.

If you experience more serious symptoms, including limited bladder and bowel control and pronounced weakness in the legs, the bundle of nerves that extends to the lowermost part of the spine may be severely compressed. This condition, called cauda equina syndrome, is much more serious than typical lumbar stenosis and requires immediate treatment.

Symptoms of Cervical Stenosis

Cervical stenosis is diagnosed less frequently than lumbar stenosis. In the cervical spine, bone spurs, ligaments, or cartilage from an intervertebral disc can intrude into the spinal canal and pinch just the nerves, causing pain in the neck and arms.

These obstructions may pinch the spinal cord itself, leading to serious neurological damage. A constricted spinal cord may not cause neck pain but rather weakness, heaviness, or numbness in the arms and hands. Severe compression of the spinal cord that restricts movement throughout the body requires immediate treatment.

Causes and Associated Conditions

For most people diagnosed with spinal stenosis, the spinal canal narrows because of degeneration in the spine that occurs as a natural part of aging. These degenerative changes most frequently affect the vertebral joints, also called facet joints, and the spongy discs that lie between vertebrae.

As the spine ages, intervertebral discs slowly lose fluid in a process called degenerative disc disease. Degeneration may cause a disc to bulge into the spinal canal, putting pressure on nerves or the spinal cord. If the outer wall of a disc breaks down completely and a disc fragment slips into the spinal canal, it’s called a herniated disc.

In addition, degeneration of the facet joints caused by osteoarthritis of the spine often leads to the development of bone spurs. These small, hard growths may protrude into the foramen or the spinal canal, constricting the exiting nerves or the spinal cord. Increased friction within joints may also irritate nearby ligaments, causing them to swell and take up more space in the spinal canal.

A facet joint can degenerate to such an extent that it no longer provides stability to the vertebra, which may slip out of place and move forward. In this condition, called spondylolisthesis, the vertebra can slip too far forward, putting pressure on the spinal cord or nerve roots.

Rarely, people are born with a narrow spinal canal or have a developmental condition that leads to a narrowing of the spinal canal. These include achondroplasia, scoliosis, and spina bifida, in which symptoms appear before age 50. Spinal stenosis may also be caused by a spine tumor.

A trauma to the spine, such as an injury from a car accident, that results in a dislocation or a fracture may also constrict nerves or the spinal cord at any point in the spine.

Medical History

In order to make an accurate diagnosis, NYU Langone doctors first ask you for information about your symptoms. This may include when you first felt pain; where the pain is located; whether you experience any heaviness, numbness, or weakness in your arms or legs; whether the pain gets worse when you move; and whether the pain is relieved when you sit down. These and other details help doctors narrow down the cause of your symptoms.

Physical Exam

Your doctor also performs a physical exam to further assess the source of pain and other symptoms. The physician looks for any restricted movement in the spine or neck and tests for weakness in the arms and legs. You may be asked to walk or bend so the doctor can see your spine in motion.

A neurological evaluation may determine whether nerve damage is contributing to your symptoms. Nerves travel through the body, affecting muscles in predictable patterns. These patterns can be used to guide your doctor in matching abnormal physical responses with particular nerves.

For example, your doctor may use a small hammer to test for unresponsive nerve reflexes in various parts of your body, which may indicate a pinched nerve. A doctor may also expose areas of your skin to stimuli—such as warm and cool temperatures—to assess whether sensation is affected.

Signs of physical weakness may also indicate nerve compression. Your doctor may ask you to use specific muscle groups in moving parts of your body to assess strengths and weaknesses. Visible muscle twitches or spasms may also suggest nerve damage.

Imaging Tests

NYU Langone doctors also use imaging tests to confirm a diagnosis of lumbar or cervical stenosis.

X-Rays

Doctors frequently recommend X-rays as a first diagnostic imaging test. X-rays allow doctors to measure the diameter of the spinal canal and detect a fracture in the spine. Additionally, stenosis resulting from a condition such as scoliosis or spina bifida can be confirmed using X-rays.

MRI Scans

Your doctor may use an MRI scan to see the ligaments, discs, and soft tissues in the spine, including the spinal cord and nerves. An MRI can also reveal if an intervertebral disc has bulged or slipped out of place. An MRI machine uses a magnetic field and radio waves to create images of your body.

CT Scans

A CT scan is a series of X-rays that combined provide more comprehensive detail about the spine than a single X-ray image. NYU Langone doctors use CT scans to confirm the development of bone spurs in the spinal canal or a fractured or displaced vertebra. CT scans can also reveal the narrowing of facet joints.

CT–Myelogram

This type of CT scan uses a nontoxic dye to provide more detailed images of the spinal canal. Before the CT images are taken, doctors use a thin needle to inject a special dye into the spinal canal. The dye moves through the spinal canal within minutes, illuminating the spinal cord and nerve roots. CT images taken while the dye is in the spinal canal provide more detail than a traditional CT scan and can help doctors confirm the cause of stenosis.

Electromyogram and Nerve Conduction Study

If you feel radiating pain in your arms or legs or experience any weakness, tingling, or numbness, an electromyogram or nerve conduction study can reveal whether these symptoms result from compressed nerves. Often, doctors perform both tests when assessing the health of nerves.

An electromyogram measures the electrical impulse along nerves, nerve roots, and muscle tissue. A nerve conduction study measures how efficiently, and how quickly, nerve impulses travel.

During an electromyogram, a doctor inserts small, thin needles—called electrodes—through the skin and into muscles that correspond to specific nerves. Doctors then ask you to move these muscles one at a time. The signals recorded when each muscle contracts can show the doctor which nerve roots are affected and whether a nerve injury has caused muscle damage.

In a nerve conduction study, a doctor adheres several small, flat electrodes to the skin over the nerve and surrounding muscle. A brief pulse of electricity emits from the electrode to the nerve, and a machine records how quickly the corresponding muscle contracts. If the muscle does not contract right away, it may indicate that the nerve is being pinched, interfering with its function.

Both tests are relatively painless, though some people feel uncomfortable with the electromyogram needles. Usually, this test takes about 15 to 30 minutes to complete.